The present invention relates to a die set, more precisely it relates to a die set comprising: an upper die; and a lower die being capable of relatively moving to and away from the upper die, wherein a metal plate having a through-hole, which is rounded by a collar with prescribed height, is provided between the upper die and the lower die, and a flange section is formed at an end of the collar by the dies.
A radiating fin, which is employed to heat exchangers for air conditioners, has a metal plate section, which is made of, for example, a rectangular thin aluminum plate, and a multiple collared holes, which are bored in the metal plate section.
In the heat exchanger, a plurality of said fins are stacked, and the collared holes of each fin are coaxially connected. Metal pipes, which are made of high heat conductive metal, e.g., copper, are pierced through the collared holes, which have been coaxially connected, so that the fins and the metal pipes can be integrally assembled. Thus, clearance between adjacent fins is almost equal to the height of the collars of the collared holes.
The fins of the heat exchanger are made by, for example, the method disclosed in U.S. Pat. No. 4,055,067. The method is shown in FIGS. 7A-7D.
In the method, firstly a thin metal plate 100 is bored and burred to form a hole 101 rounded by a projected section 102 (see FIG. 7A). Successively, the diameter of the hole 101 is enlarged and the projected section 102 is ironed to extend until the projected section is formed into a collar 104 with prescribed height (see FIGS. 7B and 7C).
Further, an upper end of the collar 104 is flared to form a flange section 105 (see FIG. 7D).
The above described fin may be manufactured by a die set shown in FIG. 8. The metal plate 100 is fed and intermittently conveyed in the direction of an arrow A. The metal plate 100 is conveyed into stages 14, 16, 18 and 200, which are set between a vertically movable upper die 10 and a fixed lower die 12, in order. Afterwards the metal plate 100 comes out in the direction of an arrow B.
The boring and the burring shown in FIG. 7A are executed in the stage 14; the ironing shown in FIGS. 7B and 7C are executed in the stages 16 and 18; and the flaring shown in FIG. 7D is executed in the stage 200.
In the die set having the stage 200, there is fixed a flare-punch 204 in an upper die 202 (see FIG. 9), so that an end part of the flare-punch 204 gets into the collar 104 of the metal plate 100, which has been mounted on a lower die 206, and forms the flange section 105 at the end of the collar 104.
The height of the collar 104 of the metal plate 100, which has passed the stage 200, is equal to distance H between the flange forming section 205 of the flare-punch 204 and an upper face of the stage 200 in the lower die 206, so that the collar height or the distance H is defined by the lowest position of the downward movement (the lower dead point) of the flare-punch 204.
Note that, the lower die 206 has a hole 208 into which the lower end part of the flare-punch 204, which has pierced through the collared hole 102, is able to get.
Conventionally, the lower dead point of the flare-punch 204 cannot be adjusted while manufacturing.
While a press machine with said die set is in operation, the die set is heated, so that the temperature of the die set rises until the heating calory and the radiating calory are balanced. By the heating, members constituting the press machine expand. With the result of the heat expansion, the lower dead point of the flare-punch 204 is changed with the lapse of time. Thus, the collar height H of starting the press machine is different from that of stopping the machine.
If multiple fins whose collar height H is not fixed, as described above, are stacked, the height of a radiating section of a heat exchanger is apt to be different in places.
The unstable manufacturing accuracy can be solved by a cooling system, which cools the press machine to maintain the temperature thereof by a fluid, e.g., oil, circulating in pipes.
However, the press machine with the cooling system must be complex in structure and large in size.
Before starting the press machine, the lower dead point of the flare-punch 204 may be adjusted to a proper position considering the heat expansion. But in this case, it is very difficult for unskilled persons to properly adjust the lower dead point. Furthermore, even if the lower dead point is properly adjusted, the lower dead point changes by the heat expansion, so that the manufacturing accuracy cannot be fixed.
Even if the die set is designed to simultaneously form, for example, three flange sections, there is a case that one or two flange sections are formed. In the case where the actual number of flange forming sections is less than the planned number thereof, unbalanced force acts on the upper die to which the flare-punches are provided, so that the upper die is slightly inclined. Even if the press machine has the cooling system, the inclination of the upper die which is caused by said unbalanced force cannot be avoided. By said inclination of the upper die, the height of the collars must be scattered in places.
To solve this problem, one of inventors of the present invention invented a die set disclosed in Japanese Patent Kokai Gazette 5-200450. The die set is shown in FIG. 10.
In the die set, there is provided a measuring sensor 226 in a lower die 206; there is provided an object member 225 in an upper die 202. When the distance between a lower face of the upper die 202 and an upper face of the lower die 206 is the shortest or when the upper die 202 reaches the lower dead point, a measuring section 224 measures the distance to the object member 225 by the sensor 226. An elevating section 210 is capable of vertically adjusting the lower die 206 so as to adjust the lower dead point of the upper die 202. A stepping motor 220 vertically moves the elevating section 210 on the basis of the distance measured by the measuring section 224.
Note that, the elevating section 210 has a plurality of fixed triangle members 212, which are fixed on the upper face of a lower base 12 and whose sloping faces are arranged on upper sides, and a plurality of movable triangle members 214, whose sloping faces are capable of respectively sliding on the sloping faces of the fixed triangle members 212.
In the die set shown in FIG. 10, if the lower dead point of the upper die 202, which has been measured by the measuring section 224, is changed or shifted with respect to an initial set position with the lapse of time, the lower die 206 is moved upward by the stepping motor 220. With this mechanism, the lower dead point of the upper die 202 can be maintained at the initial set position as much as possible, so that the collar height of the collared holes can be equal as much as possible.
However, in the die set shown in FIG. 10, the manufacturing accuracy is affected by errors in the measuring section 224, the stepping motor 220, the elevating section 210, etc., so that the scatter of the collar height cannot be fully removed. Furthermore, means for driving the elevating section 210, e.g., the stepping motor 220, and means for controlling must be provided in the die set, so the die set must be complex in structure and large in size.